Paper cassette design with irregular bottom

ABSTRACT

A sheet feeding apparatus as provided wherein the surface for supporting a stack of sheet material includes an inclined surface portion positioned between the leading edge of the stack and the feeding means. The inclined surface coacts with the feeding means to elevate the leading edge of the top most sheet away from the next adjacent sheet as it is fed from the stack. Preferably the sheet feeding apparatus comprises a reverse buckle type sheet feeder. The sheet feeding apparatus is adapted to elevate the leading edge of the top most sheet as it is being fed to thereby improve sheet separation and reduce jamming propensity.

United States Patent 1191 Patel l PAPER CASSETTE DESIGN WITH IRREGULAR BOTTOM [75] Inventor: Sumant Patel, Webster, NY.

[73] Assignee: Xerox Corporation, Stamford,

Conn.

[22] Filed: June 21, 1973 [21] Appl. No.: 372,437

52 US. Cl 271/22, 271/127, 271/170 51 1111. C1 B65h 3/06, B65h 3/46 58 Field of Search 27 1/21,22, 23-25, 271/109, 126,127, 170

[56] References Cited UNITED STATES PATENTS 3,350,089 10/1967 Niccoli 271/21 3,503,603 3/1970 Dvorak 271/23 3,687,448 12/1970 Vora 271/21 11] 3,857,558 1451 'Dec. 31, 1974 Primary Examiner-Evon C. Blunk Assistant Examiner-Bruce H. Stoner, Jr.

Attorney, Agent, or Firm-Paul Weinstein; Clarence A. Green; James J. Ralabate [57 ABSTRACT A sheet feeding apparatus as provided wherein the surface for supporting a stack of sheet material includes an inclined surface portion positioned between the leading edge of the stack and the feeding means. The inclined surface coacts with the feeding means to elevate the leading edge of the top most sheet away from the next adjacent sheet as it is fed from the stack. Preferably the sheet feeding apparatus comprises a reverse buckle type sheet feeder. The sheet feeding apparatus is adapted to elevate the leading edge of the top most sheet as it is being fed to thereby improve sheet separation and reduce jamming propensity.

10 Claims, 4 Drawing Figures PATENTED EH13 I I974 SHEET 10F 2 FIG. 3

PAPER CASSETTE DESIGN WITH IRREGULAR BOTTOM BACKGROUND or THE INVENTION This invention relates to a sheet feeding device which is suitable for use in an automatic reproducing machine, for example, a xerographic copier. The appara tus of this invention is adapted to feed individual sheets successively from a stack to a suitable mechanism which is to operate on the sheets. The invention is particularly directed to a sheet feeding apparatus of a type in which one sheet of the stack is reverse buckled to detach it from the other sheets and when so detached is fed from the stack. In accordance with this invention means are provided for increasing the elevation of the leading edge of the sheet as it is fed from the stack thereby reducing the propensity forjams to occur, such as those that occur due to the interaction of front edge snubber tabs and the lead edge of the top most sheet.

In a reverse buckle sheet feeder the rear margin of the stack is supported against the rear wall of a sheet support tray, so that the sheets are free to move only ina forward direction. Feeding means are then brought into operative contact with the uppermost sheet in the stack and a motion imparted to the sheet to first drive the sheet rearwardly against the restraining force of the rear wall of the tray. As a consequence, a longitudinal buckle is formed in the body of the sheet causing the sheet to be separated from the stack. Once separated the direction of sheet motion is reversed and the sheet is advanced forwardly through an opening in the tray and cleared therefrom prior to instituting a subsequent feeding cycle.

US. Pat. Nos. 1,054,637 granted 1913, 3,350,089 granted 1967, 3.417,988 granted 1968 and 3,687,448 granted 1972 all show and describe reverse buckle sheet feeding apparatuses wherein the support tray includes a discontinuity in the supporting surface which deforms the sheet material supported thereon. The discontinuities are employed for a variety of reasons including breaking up the stack to provide better separation and or for maintaining normal distribution of forces on each sheet of the stack regardless of the height of the stack. In each of the apparatuses disclosed in the above-noted patents the discontinuity is present below or behind the feed roll and, therefore, the discontinuities do not serve to elevate the leading edge of the top most sheet as it is being fed from the stack as in accordance with the present invention.

SUMMARY OF THE INVENTION In accordance with this'invention a sheet feeding apparatus is provided including means for supporting a stack of sheet material wherein the support means includes at least one inclined surface for deforming the sheet material supported thereon and feeding means arranged to contact the top most sheet of the stack for feeding the sheet from the stack. In accordance with this invention the inclined surface is positioned between the leading edge of the stack and the feeding ing means comprises one or more rolls. It is also preferred to employ front edge snubber tabs to maintain the alignment of the stack. The stack supporting means preferably comprises a tray or cassette wherein the inclined portion represents a bump in the bottom of the tray or cassette. Preferably the inclined surface or bump comprises a curved operative surface which deforms the stack so as to provide a raised portion in the top most sheet of the stack. The feed roll by contacting the top most sheet behind the raised portion, when viewed in the direction of feeding, coacts with the raised portion to elevate the lead edge of the top most sheet so that it will readily separate from the stack and pass over front snubber tabs. It is an object of this invention to provide an improved sheet feeding apparatus.

It is a further object of this invention to provide a sheet feeding apparatus which is adapted to elevate the leading edge of the sheet being fed.

It is a further object of this invention to provide an apparatus as above which provides improved sheet separation and reduces jamming propensity.

It is a further object of this invention to provide any apparatus as above wherein sheet separation is accomplished byreverse buckling.

These and other objects will become more apparent from the consideration of the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows schematically an exemplary xeroj graphic reproducing machine with which the sheet means so that the inclined surface coacts with the feedthe sheet feeding apparatus in accordance with this invention, during forward feeding of the sheet.

FIG. 4 shows a perspective view of a sheet feeding apparatus in accordance with this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1 there is shown by way of example an automatic xerographic reproducing machine 1 which incorporates the improved sheet feeding apparatus 2 of the present invention. The reproducing machine l depicted in FIG. 1 illustrates the various components utilized therein for producing copies from the original. Although the sheet feeding apparatus of the present invention is particularly well adapted for use in an automatic xerographic reproducing machine 1 it should become evident'from the following description that it is equally well suited for use in a wide variety of machines requiring single sheet feeding and is not necessarily limited in its application to theparticular emcopy of an original are herein represented in FIG. 1 as blocks A to E. Initially the drum 10 moves photoconcharging station A an electrostatic charge is placed unifQrmly over the photoconductive surface 11 of the drum l preparatory to imaging Thereafter, the drum is rotated to exposure station B where the charged photoconductive surface 11 is exposed to a light image of the original input scene information, whereby the charge is selectively dissipated in the light exposed regions to record the original input scene in the form of a latent electrostatic image. After exposure, drum 10 rotates the electrostatic latent image recorded on the photoconductive surface 11 to development station C wherein a conventional developer mix is applied to the photoconductive surface 11 of the drum 10 rendering the latent image visible.

The developed image on the photoconductive surface 11 is then brought into contact with a sheet 14 of final support material within a transfer station D and the toner image is transferred from the photoconductive surface 11 to the contacting side of the final support sheet 14. The final support material may be paper, plastic, etc., as desired. After the toner image has been transferred to the sheet of final support material 14 the sheet with the image thereon is advanced to a suitable fuser 15 which coalesces the transferred powder image thereto. After the fusing process the sheet 14 is advanced by rolls 15 to catch tray 16 for subsequent removal therefrom by the machine operator. The residual toner particles remaining on the photoconductive surface 11 after the transfer operation are removed from the drum 10 as it moves through cleaning station E.

The copier in accordance with this invention can also have the capability of accepting and processing copying sheets of varying lengths. The length of the copy sheet, of course, being dictated by the size of the original input scene information, recorded on the photoconductive surface 11. To this end the paper cassette 17 is preferably provided with an adjustable feature whereby sheets of varying length and width can be conveniently accommodated therein. In operation the cassette 17 is filled with a stack of final support material 18 of preselected size and the cassette 17 is inserted into the machine by sliding along a base plate 19 as shown in FIG. 4, which guides the cassette 17 into operable relationship with a pair of feed rolls 20. When properly positioned in communication with the feed rolls 20 the top most sheet of the stack 21 is separated and forwarded from the stack into the transfer station D by means of registration rolls 22.

It is believed that the foregoing description is sufficient for purposes of the present application to illustrate the general operation of an automatic xerographic copier 1 which can embody the teachings of the present invention.

Referring now to FIGS. 2 and 3 the operative elements of the present apparatus 1 are shown. In accordance with this invention the sheet feeding apparatus 1 includes means 23 for supporting a stack of sheet material 18. The term stack as it is employed in the present application includes the single last sheet which remains after the stack has been depleted and is not meant to be limited to a, plurality of sheets. A feeding means such as rolls 20 is arranged to contact the top most sheet 21 of the stack 18. It is essential in accordance with this invention that the support means 23 include an inclined surface 2 which is adapted to deform the stack 18 to provide a protuberance 24 in the top most sheet 21 of the stack. The inclinedsurface portion 2 is located on the support surface 25 at a position between the leading edge 26 of the stack 18 and the feeding means or feed rolls 20 as shown and closely adjacent to the feed roller. The feed rolls 20 coacts with the protuberance 24 caused by the inclined surface 2 so as to elevate the leading edge 27 of the top most sheet 21 as it is fed from the stack 18 therebyproviding an improved separation and improved clearance between the leading edge of the sheet so that the sheet can be fed over front snubber tabs or other like obstructions. Preferably the inclined portion 2 has a curved convex shape which provides a smoothly deformed surface or protuberance 24 in the top most sheet 21. By positioning the feed rolls 20 closely adjacent to the leading upwardly rising portion 28 of the protuberance 24 in the top most sheet the greatest advantage is taken of the beam strength of the sheet 21 for elevating the leading edge 21 thereof. In the most preferred embodiment of this invention the nip formed between the roll 20 and the top most sheet 21 is immediately adjacent the leading upwardly rising portion28 of the protuberance 24, for example, preferably within about one-half inch and more preferably within about one-fourth inch. This deflection of the sheet in the immediate area of the protuberance 24 provides the improvement in the elevation for the leading edge 27 of the top most sheet 21.

It is also preferred in accordance with this invention that the inclined surface 2 and protuberance 24 associated therewith be positioned sufficiently close to the leading edge 26 of the stack 18 so that the leading edge 27 of the top most sheet 21 after deformation about the protuberance is elevated from the next adjacent sheet 29. This distance, of course, depends on the beam strength of the sheet 21 being processed. If the inclined surface 2 is positioned too far rearwardly from the leading edge 26 of the stack 18, the beam strength of the sheet 21 will not be sufficient to maintain its leading edge 27 elevated from the next adjacent sheet 29. Preferably the leading upwardly rising portion 28 of the protuberance 24 is positioned within about 8 inches of the leading edge 26 of the stack 18 and more preferably within about 4 inches.

The invention is particularly applicable to a reverse buckle type sheet feeder as shown in FIGS. 2 and 3. In operation, the feed rolls 20 during the first segment of feeding cycle feed the top most sheet 21 rearwardly so as to form a buckle 20 which is effective to separate the top most sheet from the next adjacent sheet 29. As shown in FIG. 3, following the buckling operation, the feed rolls 20 are reversed to feed thetop most sheet 21 in the forward direction away from the stack 18.

The elevation of the leading edge 27 of the top most sheet 21 during the feeding operation as shown in FIGS. 2 and 3 is sufficient to help enable the leading edge of the sheet to clear any obstructions such as front snubber tabs 31 at the leading edge 26 of stack 18. The increased elevation provided in accordance with this invention for the leading edge 27 of the sheet 21 makes it significantly easier to clear any such obstructions and significantly reduces the tendency for snubber jams to occur, and permits broader tolerances for the thicknesses of the tips of the snubbers 31 thereby providing a substantial cost reduction.

Referring now to FIG. 4 a specific embodiment of a sheet feeding apparatus in accordance with this invention is described. The apparatus is similar in many respects to those described in US. Pat. application, Ser.

No; 255,355 now U.S. Pat. No. 3,773,316, filed May 22, 1972, and US. Pat. No. 3,731,915 issued to Guenther in 1973. The apparatus includes a pair of feed rolls 20 usually made of rubber or similar material mounted in cooperative relation to each other in front of snubber tab members 31 which assist in separating the forwardly moving-sheet 21 from the remainder of the stack 18. However, it will be appreciated that one feed roll 20 in lieu of two will operate satisfactorily. The feed rolls 20 advance the top most sheet 21 of the stack 18 over the tab members 31 and between the forwarding rolls 32 until the leading edge 27 of the advancing sheet engages the registration member or gate 33. This is achieved by a suitable endless belt or chain drive 34 which rotates the cam '35 in the direction of arrow 36. Sector gear 37 is resiliently maintained in engagement with the cam 35 by means of a suitable spring member 38. The cam 35 drives the sector gear 37 in an oscillating fashion. The sector gear 37 meshes with a pinion gear 39 to rotate the pinion gear incounterclockwise and clockwise directions. Since the pinion gear 39 and feed rolls 20 are secured to ,a common shaft 40, the feed rolls rotate in conjunction with the pinion gear as indicated by arrow 41. The'feed rolls 20 are in intermittent rotation and are adapted to engage the top most sheet 21 of the stack 18 disposed in the tray member or cassette indicated generally at 17. The tray member 17 includes a pivotable base plate 42 on which the stack 18 of sheet material is disposed. Biasing means generally indicated at 43 is mounted to engage the base plate 42 to move it in an upwardly and downwardly direction. The base plate 42 is adaptedto pivot so that the top most sheet 21 of the stack 18 engages the feed rolls 20 which are fixably attached to shaft 41 and remain stationary relative thereto. Drive 34 rotates shaft 44 having cam 45 mounted thereon. Cam 45 in turn drives cam follower 46 which is mounted on a common shaft 47 with the tab members 31. Tab members 31 thereby pivot in synchronism with the feed rolls 20 to engage and disengage the top most sheet 21 of the stack 18 at the appropriate time, i.e., shaft 47 rotates in both a clockwise and counterclockwise direction as indicated by arrow 48. Preferably, tab members 31 are self-aligning, i.e., they are suitably secured to shaft 47 to be vertically movable and laterally pivotable to position their horizontal surface squarely on the top most sheet 21 of the stack 18. Registration roll 49 is mounted on shaft 68. Cam 50 mounted in shaft 44 drives cam follower 51 which in turn causes connecting link 52 to pivot in the direction of arrow 53. Link 52 has shaft 54 and rod 55 affixed thereto. In this way shaft 54 which. has forwarding roll 56 mounted thereon is adapted to move forwarding roll 56 intoand out of engagement with an advancing sheet 21 passing over forwarding roll 56.

The advancing sheet 21 moves between the closely spaced forwarding rolls 32 and the leading edge portion thereof engages registration gate 33. Thereafter link 52 pivots to move forwarding roll 56 downwardly into engagement with the advancing sheet 21 and the registration gate 33 downwardly to disengage from the leading edge 27 portion of the advancing sheet. The sheet 21 is thereupon transferred to the image transfer station D as in FIG. 1 in a timed relationship with the image on the drum 10. It will be appreciated that the operation of the sheet feeding apparatus is controlled by driving means 34 which in turn engages the copier input drive via a suitable clutch (not shown) actuated by a suitable solenoid .(not shown) that is activated by the optical scanning system. In this manner the sheet feeding apparatus is maintained in a timed relationship with the image on the drum 10 to insure registration of the advancing sheet with the image. In accordance with this invention the base plate 42 includes the inclined portion 2 which deforms the stack 18 to provide the protuberance 24 in the top most sheet 21 which is located closely adjacent to the feed rolls 20.

In operation the base plate 42 is moved in an upwardly direction by biasing means 43 to move the top most sheet 21 into engagement with the feed rolls 20. The feed rolls 20 are rotated in a counterclockwise direction to move the uppermost sheet 21 in the stack 18 in a rearwardly direction. The rearward movement of the sheet 21 produces a buckle 30 therein and facilitates the separation thereof from the remainder of the sheets from the stack. During this portion of the operation the forwarding rolls 32 are spaced apart from one another and the registration gate 33 is pivoted in an upwardly direction to its operable position. As the sheet 21 moves rearwardly it flips from beneath the snubber tab members 31 and the tab members drop down onto the next adjacent sheet 29 of the stack 18. Then the direction ofrotation of the feed rolls 20 is reversed and the sheet 21 is advanced in the forward feeding direction over the tab member 31 until the leading edge 27 thereof engages the registration gate 33. The protuberance 24 caused by the inclined surface portion 2 in the base plate 42 coacts with the feed rolls 20 during the forward feeding portion of the cycle to provide increased elevation of the leading edge 27 of the sheet 21. This enables the sheet to readily pass over the snubber tabs 31 and substantially reduces the propensity for snubbing jams. The forwarding rolls 32 are spaced apart from one another to allow the sheet 21 to be interposed therebetween. The leading edge 27 of the advancing sheet 21 abuts the registration gate 33 and a buckle is produced therein which removes any sideways skewing of the sheet. This insures that the image transferred from the drum will be appropriately oriented on the sheet 21. After the leading edge 27 of the sheet 21 has engaged the gate member 33 and produced the slight buckle therein, the gate member is moved in a downwardly direction. The forwarding roll 56 also moves in a downwardly direction to contact and position the sheet in engagement with registration roll 49 rotating in the direction of arrow57 for a continuing advancement of the sheet 21. As the forwarding roll 56 moves in a downwardly direction to move the sheet 21 into engagement with the registration roll 49 the tab members 31 pivot base plate 42 in a downwardly direction by applying a force of sufficient magnitude to overcome the resilient force exerted thereon by biasing means 43.

In this way the feed rolls 20 only rotate about shaft 40 and do not translate relative to the machine frame, whereas the stack 18 disposed on the-base plate 42 is pivoted into and out of engagement with the feed rolls 20.

In accordance with this invention the term forwardly indicates the direction in which the sheet 21 is to be fed from the stack 18 whereas the term rearwardly indicates the opposite direction.

The inclined surface in accordance with this invention may be a homogeneous portion of the supporting surface or it may be integrally connected thereto as desired. Preferably the inclined portion extends transverse to the direction of sheet feeding so as to completely traverse the sheets of the stack. Preferably the inclined surface lies parallel to the axis of the feed rolls.

The patents and applications referred to specifically in the detailed description of this application are intended to be incorporated by reference into the description.

It is apparent that there has been provided in accordance with this invention a sheet feeding apparatus which fully satisfies the objects, means and advantages set forth hereinbefore. While the invention has been described in conjunction with specific embodiments therefore it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications and variations as fall within the spirit and broad scope of the appended claims.

What is claimed is:

l. A sheet feeding apparatuscomprising: support means for supporting a stack of sheet material on top thereof, said support means including at least one inclined surface for deforming said sheet material supported thereon to form a protuberance in the top most sheet, means coacting with said protuberance for elevating the leading edge of said top sheet as it is fed from said stack, said elevating means including feeding means arranged to contact the top most sheet of said stack for feeding the top most sheet from said stack, said inclined surface being positioned between the leading edge of said stack and said feeding means.

2.'An apparatus as in claim 1 wherein said protuberance includes a leading upwardly rising portion and wherein said feed means is positioned closely adjacent to said upwardly rising portion.

3. An apparatus as in claim 2 wherein said inclined portion has a convexly curved shape which provides a smoothly deformed surface which constitutes said protuberance.

4. An apparatus as in claim 2 wherein said feeding means comprises at least one roll.

5. An apparatus as in claim 4 wherein said elevating means includes means to deflect said sheet in the area of said protuberance to elevate the leading edge thereof, said deflecting means comprising the nip formed between said roll and said top most sheet with said nip being positioned immediately adjacent the leading upwardly rising portion of said protuberance.

6. An apparatus as in claim 5 wherein said nip is within about one-half inch of said upwardly rising portion of said protuberance.

7. An apparatus as in claim 5 wherein said inclined surface and associated protuberance are positioned sufficiently close to the leading edge of said stack so that the leading edge of said top most sheet after deflection about said protuberance is elevated from the next adjacent sheet as it is fed from said stack.

8. An apparatus as in claim 7 wherein the leading upwardly rising portion of said protuberance is positioned within about 8 inches of the leading edge of said stack.

9. An apparatus as in claim 8 wherein said sheet feeding apparatus comprises a reverse buckle sheet feeder wherein said feed roll is adapted to advance said top most sheet first rearwardly to form a buckle and then forwardly to feed said sheet from said stack.

10. An apparatus as in claim 9 further including snubber means contacting the leading edge of said top most sheet. 

1. A sheet feeding apparatus comprising: support means for supporting a stack of sheet material on top thereof, said support means including at least one inclined surface for deforming said sheet material supported thereon to form a protuberance in the top most sheet, means coacting with said protuberance for elevating the leading edge of said top sheet as it is fed from said stack, said elevating means including feeding means arranged to contact the top most sheet of said stack for feeding the top most sheet from said stack, said inclined surface being positioned between the leading edge of said stack and said feeding means.
 2. An apparatus as in claim 1 wherein said protuberance includes a leading upwardly rising portion and wherein said feed means is positioned closely adjacent to said upwardly rising portion.
 3. An apparatus as in claim 2 wherein said inclined portion has a convexly curved shape which provides a smoothly deformed surface which constitutes said protuberance.
 4. An apparatus as in claim 2 wherein said feedIng means comprises at least one roll.
 5. An apparatus as in claim 4 wherein said elevating means includes means to deflect said sheet in the area of said protuberance to elevate the leading edge thereof, said deflecting means comprising the nip formed between said roll and said top most sheet with said nip being positioned immediately adjacent the leading upwardly rising portion of said protuberance.
 6. An apparatus as in claim 5 wherein said nip is within about one-half inch of said upwardly rising portion of said protuberance.
 7. An apparatus as in claim 5 wherein said inclined surface and associated protuberance are positioned sufficiently close to the leading edge of said stack so that the leading edge of said top most sheet after deflection about said protuberance is elevated from the next adjacent sheet as it is fed from said stack.
 8. An apparatus as in claim 7 wherein the leading upwardly rising portion of said protuberance is positioned within about 8 inches of the leading edge of said stack.
 9. An apparatus as in claim 8 wherein said sheet feeding apparatus comprises a reverse buckle sheet feeder wherein said feed roll is adapted to advance said top most sheet first rearwardly to form a buckle and then forwardly to feed said sheet from said stack.
 10. An apparatus as in claim 9 further including snubber means contacting the leading edge of said top most sheet. 